Use CSS to hide reply forms

We were using inline styles and passing local variables around, while
the rule we were following is very simple: it's only hidden if it's a
form to reply to a comment.

app/views/comments/_comment_tree.html.erb

@@ -27,7 +27,6 @@
           <% elsif !valuation || can?(:comment_valuation, commentable) %>
             <%= render "comments/form", { commentable: commentable,
                                           parent_id: nil,
-                                          toggeable: false,
                                           valuation: valuation } %>
           <% end %>
         <% else %>